Method of casting concrete pipes and the like



Oct. 17, 1950 B. J. UKROPINA METHOD-70F CASTING CONCRETE PIPES AND THE LIKE Filed Oct. 1, 1949 INVENTOR. fioz/ane J U/GQOP/NA fiatentecl Oct. l- 7 1956 ivmriion 70F 2,526,174 QASTINGGONGRETE execs AND THE LIKE was J. Ukropiiia, Baldwin park, ca-iii, as-

signor to United Concrete Pipe Corporation; BaldwinPark, Caliil, a corporation of Cali fornia Application October 1, 1949, Serial N0.-1119,053

This invention relates to a method of casting or molding concrete, andis particularly advantageous in casting or molding concrete pipe and similar concrete structures.

A primaryobject of the invention'is to provide- I a method of casting or molding concrete structures in such amanner asto' obtain concrete containing the maximumamount of coarse aggregate and producing concrete ofa given .strength with a minimum amount v.of' cement. To designers Of structural concrete it is general knowledgethat certain factors influence and detergmine the-strength of the structured. e.,1the qualjity of the aggregate employed, the proportions 'used, the maximum size of. aggregate particles used, the quantity of cement, the quantity f water used per unit volume, the absence of voids in the {mass,'and thedensity. J

Heretofore, methods .have been developed vfor casting or molding concrete wherein the mold or jfOIl'Il is vibrated after having been filled with the 7 ;mixed concrete. The vibration tends to consolidate the aggregate particles and to increase the strength of the mass by the elimination of voids and increasing the density of the concrete. However, when the concrete is'vibrated the larger or denser aggregate particles tend to settle toward thebottom of the mold displacingwater and the finer aggregate particles upwardly so that when the concrete is cured or allowed to set the larger aggregate particles will predominate in the lower part of the mold whereas at the top 3 Claims. (01. 25-155,) Y

. in the mad :as a lean of its having been vibrated;v 1 "Fig-:3 illustratesqthe mold and concrete after corrective-measures have been taken to fill the mold andenable :a uniform distribution of large aggregate particles to beobtained; and

-Eig; 4 illustrates the condition of the mold and concrete after itL-has been vibrated a second-time.

1 Referring wherein similar reference characters designate to "the accompanying drawings similar p-artsthroughout, the mold illustrated is -12, simplified1formwoi mold for producing concrete q'a'cke't i i supported-on a base i2.

consistingof ;an inner core iii and an outer It will be appreciated, however' that the present invention is not confined to the making of concrete pipe but :pine

' inn-ay' be fused in producing other concrete struc- "tures, and :even when used to make concrete pipe there may be considerable variation in (the details of construction of the mold.

In -,accor.dance with :the present invention the V mold -is ;partially filled-withconcrete i 3 composed of the mold only the finer aggregates will be I present. This results in concrete pipe and similar concrete structures being stronger at the lower part than at the top whereas, it is desired to have such structures of uniform strength from bottom to top. I

The improved method is designed to promote such uniformity and yet retain all of the advantages attendant to vibrating the mold in order to eliminate voids, consolidate the mass, and inof selected proportions of heavy or large-sized aggregate, such as rock, smaller aggregate such as pea gravel, sand, cement, and Water. These ingredients of the concrete are thoroughly mixed together in any suitable manner such as by a concrete mixer, and when mixed, the mixture is poured or otherwiseplaced in the mold so as to fill it to a point near but definitely below the top of the mold such as is indicated by the level l4. When the mold is thus partially filled it is vibrated in an suitable manner such as by a vibrator applied toor attached to the jacket ii. An means for vibrating the mold and its contents so as to consolidate the particles and to work out air pockets or voids may be employed.

Whenv the mold has been adequately vibrated the concrete therein will be found to be in the condition somewhat as is illustrated in Fig. 2, wherein the larger or heavy aggregate particles have settled toward the bottom of the mold displacing'the water, cement, sand, and finer aggregate particles upwardly. The result is that when the mold is merely vibrated the lower portion of the concrete casting has an adequate supply of the large or heavy rock particles which contribute materially to the strength of the casting. However, the upper portion of the concrete casting will be composed of only sand and small rock particles, and consequently, the upper portionis relatively weak. In order to correct this separation resulting from the vibration I com- 'plete the filling of the mold by addingthereto a mass indicated at I5 composed principally of large or heavy rock nly. This large rock or heavy aggregate may have been mixed with cement and water or it may consist merely of Wetted or even dry rock. The added mass contains very little, if any, sand or pea gravel. The added mass i5 thus initially occupies a position in the mold overlying the upwardl displaced sand and pea gravel indicated at [6 on Fig. 2, and the mold is thereafter vibrated a second time. The added mass [5, in the course of the vibration, also tends to settle and to displace the cement, sand, and pea gravel l6 upwardly therethrough. However, as the amount of the mass l5 that is added to the mold to fill it is relatively small, it is ordinarily not necessary to vibrate the mold the second time to any great extent and at all events vibration of the'mold the second time is discontinued as soon as it is apparent that a fairly uniform mixture is obtained between the heavy aggregate l5 and the fines at 6. As a result, the final mixture in the mold, indicatd at I! on Fig. 4, has heavy or large-sized aggregate distributed substantially uniformly therethrough so that the pipe or other structure will be of substantially uniform strength from bottom to top. It will be appreciated that b this method all of the advantages of vibrating the mold are retained in that air pockets and voids can be effectivel worked out and a dense mass secured.

It will also be appreciated that a relatively large amount of heavy aggregate can thus be introduced into the concrete to promote the V strength and that in so doing, only a minimum point near but below the top of the mold with wet concrete, vibrating the mold and then filling the remainder of the mold with principally large-sized aggregate and again vibrating the mold whereby the cement and fine aggregate which tends to collect at the top of the concrete initially placed in the mold as a result of the first vibration will tend to be displaced upwardly through the added aggregate and the article produced will have the large-sized aggregate distributed therethrough substantiall uniformly from bottom to top.

2. The method of casting a concrete article so as to have substantiall uniform consistency from bottom to topwhich includes partially filling a mold with wet concrete composed of cement, sand, pea gravel, and rock, vibratin the mold and thereafter adding to the mold rock with little if any pea gravel or sand and cement and again vibrating the mold whereby the cement, sand, and pea gravel which collected at the top of the concrete as a result of the first vibration will be displaced upwardly through the added rock during the second vibration, producing a concrete article of substantially uniform consistency.

3."The method of casting a concrete object so as to have substantially uniform consistency from bottom to top which includes partially filling a mold with concrete composed of wet cement, sand, and rock, vibrating the mold and thereafter filling the mold with wet cement and rock only and again vibrating the mold whereby the sand and cement which collected at the top' N 0 references cited. 

